Technological advances in propellantry have led to the development of a variety of active, self-deflagrating binders, of the difluoroamino type, for use in ultrahigh-burning rate, high-energy, composite propellants. However, these propellants tend to have pressure exponents near unity at the motor operating pressures which are characteristic of the advanced interceptors, and according to the propulsion subsystem design optimization study which was carried out, a pressure exponent in excess of 0.7 would be unacceptable for use in advanced interceptors. If the pressure exponent is in excess of this value, the thickness of the motor case would have to be considerably increased, with the result that the corresponding weight of the interceptor would be unnecessarily excessive.
The only readily-available methods for effecting some reduction of pressure exponent is to reduce the ammonium perchlorate content or resort to the use of ammonium perchlorate of larger weight-mean-diameter. These approaches are unacceptable because they adversely affect the burning rate. Burning rate promoters have been found to have little effect on the pressure dependence of the burning rate at these higher pressures. Similarly, the presence of aluminum has been found to have little effect.
Advantageous to the propellant performance parameters would be a means of effecting the pressure exponent without adversely affecting other desirable characteristics such as burning rate.
An object of this invention is to provide a method of controlling the pressure exponents of composite missile and rocket propellants.
A further object of this invention is to provide a method of lowering the pressure exponent of a composite rocket propellant to make the propellant acceptable for use in advanced interceptors wherein the weight and burning rate of the propellant are optimized for performance criteria.